Hydraulic press operating circuits



May 1, 1934. w. ERNST I 1,956,758

HYDRAULIC PRESS OPERATING CIRCUITS Filed Oct. 19, 1931 2 Sheets-Sheet lMay l, 1934. w. ERNST 1,956,758

HYDRAULIc PREss OPERATING CIRCUITS Filed 00T.. 19l 1931 2 Sheets-Sheet 2I lig@ IW" g- Patented May 1, 1934 UNITED STATES HYDRAULC PRESSOPERATING CIRCUITS Walter Ernst, Mount Gilead, Ohio, assignor to TheHydraulic Press Manufacturing Company,

Mount Gilead, Ohio Application October 19,

13 Claims.

This invention relates to hydraulic press operating circuits and moreparticularly to valve mechanism for controlling the admission andrelease of pressure fluid to the press cylinder or cylinders.

In my copending application Serial Noi 524,692, filed March 23, 1931, Ihave disclosed a press operating circuit so arranged that when apressing stroke has been completed, the pump will exhaust part of thefluid from the main cylinder prior to opening of the surge valve, theeffect being that pressure in the cylinder is reduced to such an extentthat the surge valve can be subsequently opened against this reducedpressure without danger of a shocks occurring. I have found that theoperating speed of the press and consequently its production capacitycan be materially increased by providing means for augmenting the actionof the pump in relieving the pressure in the main cylinder prior to theopening of the surge valve. In my prior arrangement, the rate at whichmain cylinder pressure is relieved is dependent entirely upon the rateof discharge of the pump, and since such rate is usually constant, it isnot possible in the prior arrangement to vary the rate of main cylinderpressure release, and consequently the operating speed of the press cannot be varied without changing the speed of the pump.

An object of the present invention is to provide a novel arrangement ofpressure release valve means for effecting controlled augmenting of theaction of the pump in the release of pressure fluid from the maincylinder prior to the opening of the surge valve. A further object is toprovide anovel by-pass valve mechanism for effecting return of the pumpdischarge to; a reservoir or the like during the release of pressurefluid by the release valve referred to. Other objects will becomeapparent from a reading of the following description, the appendedclaims, and the accompanying drawings, in which:

Figure 1 is a diagrammatic view of a press operating circuit, certainparts being shown in section;

Figure 2 is a central vertical sectional view of a surge valve drawn toan enlarged scale;

Figure 3 is a view in front elevation of a press and certain oi thevalves and pipes connected thereto in accordance with the invention;

Figures 4, 5 and 6 are vertical sectional views of a release valve and aby-pass valve, each of these figures showing the positions occupied bythe valves at diierent times during an operating cycle; and

1931, Serial N0. 569,785 (Cl. 138-17) Figure 7 is a detail sectionalview of a control valve shown in closed position.

A practical embodiment `of the invention is illustrated in theaccompanying drawings which show a hydraulic press A of the downwardpressure kind adapted to be operated by means of a reversible flowcircuit including,` in the present instance, a radial reversible flowpump B of a well known kind, anda surge tank or reservoir C mounted ontop of the press. It will be understood that the reversible ow type ofpump is shown by way of example and that a unidirectional discharge pumpprovided with a suitable reversing valve or valves may also be employedin carrying out the invention.

The press A includes a. base 1, a press head 2 connected to the base bystrain rods 3 and a platen 4 mounted for reciprocatory movements on thestrain rods. A main ram 5 is`connected to the platen and is mounted formovement within a main cylinder 6 having a main pressing chamber 7, andtwo doublevacting auxiliary rams .8-8 are mounted for reciprocation inauxiliary cylinders 9-9, each of the latter having an auxiliary pressingor booster chamber 10 above the associated ram 8 and a ram returningchamber 11 below the ram. Rods 12-12 extend from the platen into therespective auxiliary cylinders for connecting the platen to theauxiliary rams 8 8.

A surge valve D of the kind disclosed in my copending application SerialNo. 501,994 referred to above is provided for effecting relatively opencommunication between the pressing chamber rI and the tank C.

The surge valve includes a cylindrical valve casing 13 positioned in anopening 14 in the top of the cylinder 6 and extending downwardly intothe cylinder, the casing being provided with a peripheral flange 15positioned in a seat 16 on the top of the cylinder. The valve casing isclamped in place by means of a clamping ring l'l which forms part of aseparate casing member 18 disposed directly above the valve casing 13and which is drawn downwardly against the flange 15 by means of suitablesecuring means such as bolts 19.

The valve casing 13 is formed with a bore 20, the upper end portion ofwhich is of reduced diameter. This bore faces directly up toward thesurge tank and communicates therewith by means of a plurality ofopenings 21 in the separate casing member 18. The bore communicates withthe main cylinder by means of a plurality of radial passages 22extending through the casing and lying in a common horizontal planedisposed substantially at the vertical center of the casing 13. A valveelement 23 is mounted for vertical sliding movements within the bore andis provided with a plurality of vertically extending ribs or wings 24which cooperate with the reduced upper portion ofthe bore for guidingthe valve element. This element is formed with a seat engaging surface25 which is tapered outwardly and downwardly and which is adapted toseat upon a peripheral seat 26 formed in the bore 20, the seat beingsimilarly tapered outwardly and downwardly, and bein'g disposed aboveand immediately adjacent to the .radial passages 22.

The lower part of the valve element 23 is hollow and accommodates aspring 27 interposed between a plate 28 secured to the lower end of the`casing 13 and a spring seat 29 formed in the hollow part of the valveelement. The plate 28 is perforated as at 30 and is provided with aspring centering rib '31. The spring 27 is just strong enough tomaintain the valve element in its upperposition against its own weightand is readily yieldable to permit the element to move downwardly lwhenthe pressure'on the lower side thereof is slightly` less than that onthe top side.

In operation, when the platen and main and booster-'rams 'are beingmoved downwardly under the action 'of high pressure fluid directed tothe booster chambers only, as will be described, the va'catng'of themain cylinder by the main ram will tend to create a suction in thiscylinder. Assoonvas this takes placejthe static pressure due .to "thehead V-of"11uid lin the surge tank will 'move the valve element 23downwardly and iiuid will f lo'wv Idownwardly from the surge tankthrough the openings 21, the spaces between the ribsv 24 andthence'through the radial passages 22 and into the cylinder. It will beobserved that 'with'the exception of the change from downward to outwardilow at the plane of the radial passagesj22,` thef'uid has 'a direct andunobstructed path over which to travel in passing from the surge tank tothe cylinder so that a minimum of resistance to fluid flow is offered.The drag on the descent 'of the platen and rams usually due torestricted owis therefore reduced to a minimum and` more eicientoperation of the press is made possible.

In certain kinds of press operating circuits, such `as thatl'illustrated in the accompanying drawings, itis necessary that thesurge valve be opened when fluid is introduced into the pushbackcylinders to eiTect a return movement of the platen. This isnecessary in order to provide fend of the plunger 31 and the top face ofthe bushing, this spring serving to normally maintain the plunger out ofcontact with the top of the movable valve element 23. When a pressingstroke has been completed, fluid under pressure is admitted to thechamber 33 to act on the plunger 31 for forcing the latter downwardly toengage and open the surge valve element 23. Since the surge valve ispreferably large in order to provide for most eicient prefilling andexhausting of the main cylinder, considerable force would be required toopen the valve against the high pressure in the main cylinder.

In accordance with the present invention a novel circuit arrangementincluding a pressure release valve is provided for effecting a releaseof pressure fluid from the main cylinder prior to the opening of thesurge valve. l

The circuit shown in the accompanying drawings and arranged inaccordance with the present invention includes the press A, the pump B,the surge tank C and connecting piping including a novelarrangement ofvalve mechanism to be described. A pipe 37 leads from one side of thepump to the booster chambers 10 of the auxiliary cylinders 9 forsupplying uid under pressure to drive the platen downwardly during theiirst part of a pressing stroke. A'branch pipe 37a leads from the pipeI37 to a control valve E, and a second branch pipe 37b in turn leadsfrom the valve E to the pressing chamber 7 of the main cylinder.

The valve E includes a casing 38 and a piston valve element mountedtherein for vertical sliding movements, this valve element 'comprisingspaced heads 39 and 40 connected by a reduced portion 41 and a stem 42extending through the bottom end of the valve casing. A spring 43interposed between the bottom end ofthe casing and the head 40constantly urges the piston valve to its upper position, i. e., theposition shown in Figure 7, this upward movement of the piston valvebeing limited by a collar 44 on the stem 42 which is adapted to engagethe lower end of the valve casing. The stem 42 extendsl downwardly andslidably through a lug 4,5 on the platen and at its lower end isprovided with a head 46 adapted to be engaged by the lug 45 when theplaten reaches a predetermined point during its downward travel, afterwhich continued movement of the platen will serve to `move the pistonvalve from its Figure 7 to its Figure l position.

When the valve is in its upper and Figure 7 position, the flow throughthe pipe 37b is cut off by the head 40, which it will beobservedconstitutes the actual flow controlling part of the valve, the head 39serving to balance the valve and also serving a further purpose to belater described.

In operation, assuming the pump to be discharging through the pipe 37,fluid will be delivered to the upper ends of the auxiliary cylinders bymoving the platen downwardly, no fluid being delivered by the pump tovthe main cylinder at this time because of the pipe 37b being cut offfrom communication with the pipe 37a by the valve head 40. Duringdescent of the platen, fluid will be drawn from the surge tank into themain cylinder through the medium of the surge valve D to effect thedesired prell of the cylinder. When the platen has reached apredetermined point during its downward travel, the piston valve of thecontrol valve E will be moved to its Figure l position in the mannerdescribed above, so that iluid will be delivered from the pipe 37through the pipe 37a, the valve E, and the pipe 37b to the main cylinderas well as through the pipe 37 to the booster cylinders, after which thepressing stroke will be completed in the usual manner.

A pipe 47 is connected to provide communication between the oppositeside of the pump and E..-

the ram returning chambers 11 of the auxiliary cylinders, and a branchpipe 47a provides communication between the platen returning chambersand surge tank, a check valve 48 being connected at the end of thebranch pipe 47a and be- Lshock.

ing a'rangedto permit ilow of fluid from the tank into the branch pipe47a, but not in the reverse direction. A branch pipe 49 connected to thebranch 47a provides communication between the latter and the chamber 33of the casing 18 disposed above the surge valve, the arrangement beingsuch that the chamber 33 is-always under the same fluid pressure as arethe ram returning chambers of the auxiliary cylinders.

A branch pipe 50 leads from the pipe 47a to one end of the casing 51of apressure release valve F which is arranged to control directcommunication between the pressing chamber 7 and the tank or reservoir.This valve includes the casing 51 and a balanced piston valve mountedtherein for sliding movements and comprising spaced heads .52, 53connected by a reduced portion 54 and a spring 55 interposed between thehead 53 and the adjacent end of the casing for urging the piston valveto its Figure 1 position. At an intermediate point the casing is formedwith an internal annular passage 56 with which communicates a pipe 57connected to the pressing chamber and also a pipe `58, the purpose ofwhich will be later described. A second annular passage 59 is formed inthe valve casing to the left of the annular passage 56 asviewed inFigure 1 and communication between this passage and the surge tank isafforded by means of the pipe 60 interposed in which 'iis an adjustablechoke valve 6l which is adapted to be adjusted to variably restrict flowof fluid through the pipe 60. Communication between the pipe 57 and thepipe 60 is controlled by the head 53 of the piston valve, it being notedthat when said valve is in the position shown in Figure 1 communicationbetween the pipes 57 and 60 is cut oil, while when the valve is moved tothe left to its Figures 5 and 6 position, the pipes named communicatewith each other. A vent 61a is 'formed in the end of the valve casing toprevent trapping of air or fluid therein.

The choke valve 61 functions to prevent fluid under pressure fromescaping from the main cylindex' so rapidly as to cause an objectionableIt is desirable that fluid be released through the valve F in order toaugment the action of the pump in relieving pressure in the maincylinder, but if the release took place too suddenly, a shock mightoccur. By adjusting the choke valve 61 the rate of release through thevalve G may be fixed so that such shocks will be prevented and yetthespeed of pressure relief will be considerably higher than that due tothe action of the pump alone.

A pipe 62 is connected at one end to the valve casing 51 adjacent theright hand end thereof, and at its other end is connected to communicatewith the interior of the casing 63 of a by-pass valve G, this valvecomprising the casing 63, a

'piston valve comprising spaced heads 64, 65 ccnnected by a reducedportion 66 and a spring 67 interposed between the head 65 and the righthand end of the casing. The pipe 58 previously referred to leads fromthe release Valve to the left hand end of the by-pass -valve G foradmitting fluid under pressure from the release valve to the spacebetween the head 64 of the by-pass valve and the adjacent end of thecasing 63. A choke valve 68 isinterposed in the pipe 58 for restrictingflow of fluid therethrough, this valve being preferably adjusted topresent more resistance to flow of fluid than does the choke valve 61,for a purpose to be pointed out.

The by-pass valve G serves to control dislcharge of the pump to thesurge tank. Normally the'valve head 65 is-disposed in its Figure 4 andFigure 6 position to cut off communication between the pipe 62 and thesurge tank. When moved to its Figure 1 and Figure 5 position, in amanner to be described, communication between the pipe 62 and the surgetank is provided for. However, in order that the pump discharge be,by-passed to the surge tank, it is also necessary that the head 52 ofthe pressure release valve be moved to the left to its Figure 5 andFigure 6 position, so that fluid may flow from the branch pipe 47athrough the branch 50 and pipe 62 into the casing 68 of the by-passvalve.

As will be later set forth, it is desirable that the control valve E bemaintained open during a return stroke of the platen. To this end abranch pipe 69 is connected from the branch pipe 47a to the upper end ofthe control valve casing 38, While fluid is being delivered through thepipe 47 to the platen returning chambers 11, fluid pressure will beexerted through the branch pipe 47a and the pipe 69 on the top of thehead 39 thereby holding the piston valve down in its Figure 1 position.It will be understood that in the illustrated embodiment of theinvention, the press is reversed by reversing the direction of flow offluid through the pump B. The pump is provided with a suitable flowcontrol device 70 which forms no part of the present invention, andsince several kinds of devices for controlling the direction and volumeof ow through radial pumps of the type illustrated are Well known in theart, the details of the device 70 are not shown or described.Whereautomatic operation of the press is desired, an arrangementembodying the present invention may include automatic pump controlmechanism of the kind disclosed in my United States Patent No.1,711,378, issued April 30, 1929.

In order that the functions of the circuit and various included valvemechanism comprising the invention be readily understood, a completeoperating cycle of the circuit described above will be briefly setforth. It will be assumed that the platen is in its upper position andthat the pump is on neutral, i. e., set for no discharge. In thisposition of the platen, the surge valve will be closed as shown inFigure 2, the control valve E will be in its upper position, as shown inFigure 7, the release valve F and by-pass valve G will be in therespective positions shown in Figure 4. To produce a working stroke ofthe platen, the pump is set to discharge through the pipe line 37. Thepump will draw uid from the surge tank through the check valve 48 andthe branch pipe 47a and also from the platen returning chembers 1lthrough the pipe 47. Fluid will be delivered to the booster chambers 10of the auxiliary cylinders by means of the pipe 37, and the platen willthen be moved downwardly under the action of the auxiliary rams 8. Whenthe lng 45 of the platen engages the head 46 on the control valve stem42, the control valve will be opened, i. e., will be moved to its Figure1 position. Fluid will then flow from the pipe 37 through the branchpipe 37a, the control valve E and the branch pipe 37b into the maincylinder, producing a rise of pressure therein and acting to close thesurge valve. The platen will then be driven downwardly under thecombined action of the main and auxiliary rams.

When the desired pressing action has been effected, the pump is reversedso as to deliver fluid in the opposite direction, that is, through thepipe 47 to the ram returning chambers l1 for raising the latter and theplaten. At this time, the pump will draw fluid through the pipe 37 fromthe booster chambers 10 of the cylinders 9. Since the valve E' is heldopen immediately after reversal of the pump, the latter will also drawfluid from the main cylinder through the pipe 37b, the valve casing 38,the pipe 37av and the pipe 37. When the pump is arranged to dischargethrouglr the pipe 47, it will likewise force pressure fluid through thebranch pipe 47a andthe branch 49 into the chamber 33 of the casing 18above the surge tank tending to force the plunger 31 downwardly to openthe valve 23. However, immediately after reversal of the pump, the fluidin the pressing chamber 7 is under very high pressure which, actingagainst the lower face of the valve 2'3, opposes downward movementthereof so that the plunger 31, which is of relatively small area ascompared with the valve element 23, can not act to open the surge valve.Fluid pressure will, however, be exerted through the branch pipe 47a andthe branch pipe 50 to act on the right hand end of the head 52 of thepressure release valve, thereby forcing the latter to the left againstthe urge of the spring 55 untilv the valve has reached the positionshown in Figure 5. Fluid under pressure in the pressing chamber 7 willthen be released therefrom through the pipe 57, the release valve F, thepipe 60 and the choke valve 61, this valve having been adjusted to.present sulcient resistance to the flow of fluid through the pipe 60 toeffect the desired rate of release of pressure fluid from the chamber 7.The high pressure existing in the pressing chamber will be transmittedthrough th'e pipe 57, the casing of the release valve, the

pipe 58 and the choke valve 68 and will act on the head 64 of theby-pass valve, so as to move the latter to the position shown in Figure5 which figure shows the release valve and by-pass `'valves in thepositions occupied immediately after reversal at the end of a pressingstroke. At this time and during release of pressure fluid from thechamber 7, fluid discharged by the pump will be by-passed to the surgetankthrough the "medium of the branch 47a., the branch 50, the

pipe 62, the interior of the by-pass valve G and the passage 63 in thecasing of thsvalve. It willv be noted that in order to effect by-passingof the pump discharge, it is necessary that the pressure existing in thepressing chamber move the by-pass valve G to its open or Figure 5position and that also the pressure existing in the returning chambers-11, and hence in the pipe 50, maintain the release valve F in its openor Figure 5 position. In other words, the by-passing of the pumpdischarge is dependent upon the pressures existing in both the pressingchamber and the ram returning chambers. The pressure in the pressingchamber 7 will gradually drop, fluid being released from said chamberthrough the pipe 57, the release valve F and the pipe 60, andconsequently the pressure acting onthe head 64 of the by-pass valve willeventually drop to such a point as will enable the spring 67 to move thepist-on valve of the by-pass valve to its Figure 6 position wherein thehead 65 cuts ofi fluid through the pipe 62. The choke valve 68 in thepipe 57 is so arranged as to maintain the piston valve of the by-passvalve open in its Figure 5 position until the pressure in the pipes457and 60 has been reduced to such a point as will permit the pressureactuated plunger 31 to open the surge valve and place the pressingchamber 7 in communication with the surge tank. The pump will then nolonger discharge fluid through the by-pass valve, but will. deliverfluid to the platen returning chambers l1 to move the auxiliary rams andthe platen upwardly, fluid in the pressing chamber being expelledthrough the surge valve to the tank. At this time, fluid under pumppressure will be conducted through the branch pipes 47a and 69 to theupper end of the control valve E, and acting upon the head 39 thereofwill maintain the valve in its open or Figure 1 position. With thecontrol valve open, the surplus `fluid containedv in the upper ends ofauxiliary cylinders will escape through the pipe 37 and branchv pipe37a, the control valve casing, the branch pipe 37b, the main cylinderand the surge valve, finally passing back to the surge tank.

When the ram has reached the top. of its stroke, the pump will then bereversed so as to deliver fluid under pressure through the pipe 37.Pressure in the branch pipe 47a and consequently in the upper end of thecontrol valve will then drop, permitting the spring 43 to return saidvalve to its closed position, as shown in Figure 7. At the same time,the spring 55 will move the piston valve of the release valve to itsFigure l position, since the pressure in the pipe 50 will have dropped.The pump will then draw fluid through the check valve 48 and the branchpipe 47a and will deliver fluid under pressure through the pipe37.causing the ram to be moved downwardly, and a second pressingoperation will be completed in the manner already described.

In some hydraulic presses, the first part of the pressing stroke iseffected by a gravitational descent of the platen, no booster cylindersbeing provided. It is obvious that the pressure release valve andby-pass valve of the present invention can be used toeffect the sameresults when connected in circuit with such a press as they do in thecircuit already described. For example, in a modification of the circuitpreviously described, the upper ends of the auxiliary cylinders 9--9 areopen to the atmosphere and the pipes 37a and 37b and the valve E areomitted; the pipe 37 being directly connected to the main or pressingchamber by means of a pipe 37e shown in dotted lines in Figure 1. Inoperation, with the modified form of circuit, the pump will deliverfluid to the pressing chamber 7 during' the entire pressing stroke, theprefilling of the chamber being effected in part by the pump and in partby the gravitational descent of the ram and consequent flow of fluidfrom the surge tank through the surge valve D. When high pressure hasbuilt up in the pressing chamber and the pump reversed, the pressurerelease Valve F and the by-pass valve will function in the same manneras was set forth in connection with the circuit previously described asincluding the booster chambers.

From the foregoing, it will be apparent that in accordance with myinvention, it is possible to obtain a more rapid release of pressurefrom the main cylinder than has heretofore been possible, andconsequently the operating speed of the press is increased. By virtue ofthe adjustable choke valve 61, it is possible to regulate the operatingspeed without varying the rate of discharge of the pump. The form of theinvention shown and described herein is considered a practicalembodiment of the invention, but it will be understood that variousmodifications and changes may be made in the actual structure disclosedwithout departing from the spirit of the invention as defined in theappended claims.

1. The combination with a hydraulic press having cylinder meansincluding pressing and ram-returning chambers and cooperating ram meansmounted therein for reciprocatory movements; of a pump; mea-nsconnecting said pump with said cylinder means -for furnishing pressurefluid to said chambers; a reservoir; a surge valve for controllingcommunication between said reservoir and pressing chamber; a pressurerelease valve connected to said pressing chamber andbeing responsive topressure in said ram-returning chamber for effecting release of pressureuid from said pressing cylinder prior to opening of said surge valve;and a by-pass valve connected between said returning chamber and saidreservoir and being responsive to pressure inv said pressing cylinderfor electing discharge oi the pump to the reservoir during release ofpressure'from said pressing chamber and prior to opening of said surgevalve.

2. The combination with a hydraulic press having cylinder meansincluding pressing and ramreturning chambers and cooperating ram meansmounted therein for reciprocatory movements; of a pump; means connectingsaid pump with said cylinder means for furnishing pressure iluid to saidchambers; a reservoir; a surge valve for controlling communicationbetween said reservoir and pressing chamber; a pressure release valveconnected to said pressing chamber and being responsive to pressure insaid ram-returning chamber for eiecting release'of pressure fluid fromsaid pressing cylinder prior to opening or said surge valve; achokevalve in series with said pressure release valve and restrictingflow therethrough; a pressure responsive by-pass valve connected betweensaid returning chamber and said `reservoir; a hydraulic connectionbetween said pressing chamber and said by-pass valve; and a second chokevalve interposed in said connection and offering less restriction tofluid flow than does said first namedchoke valve.

3. The combination with a'hydraulic press including cylinder meanshaving pressing and ram-returning chambers and ram means mounted thereinfor reciprocatory movements; of a pump; a reservoir; means forming ahydraulic circuit with said pump, said reservoir and-said cylinderchambers for operating said ram means;

" a surge Valve for affording communication between said pressingchamber and said reservoir; a pressure release valve connected betweensaid pressing cylinder and said reservoir and being operable to openposition by pressure in said returning chamber; and a oy-pass valveconnected between said returning chamber and-said reservoir and beingoperable to open position by pressure in said pressing chamber.

4. The combination with a hydraulic press including cylinder meanshaving a pressing chamber and a ram-returning chamber of less capacitythan said pressing chamber, and cooperating ram means; of a reservoir; asurge valve for controlling communication between said pressing chamberand said reservoir; a pump; a hydraulic connection between saidreturning chamber and said pump through which said pump is arranged todischarge iluid during a return stroke; a hydraulic connection betweensaid pressing chamber and said pump through which fluid in said pressingchamber is discharged partially to said pump during a return stroke; apressure release valve connected to said pressing chamber for augmentingthe discharging action of said pump prior to opening of said surgeValve; and bypass valve means connected between' said returning chamberand said reservoir and being controlled by pressure in both the pressingand return chambers.

5. The combination with a hydraulic press including a platen, a maincylinder and cooperating main rm connected to said platen, auxiliarycylinder means having booster and ramreturning chambers, double-actingauxiliary ram means therein, and a connection between said auxiliary rammeans and said platen; of a reservoir; a surge valve connected betweensaid main cylinder and reservoir; a pump; a hydraulic connection betweensaid pump and said ram-returning chamber; a second hydraulic connectionbetween said pump and said booster chamber; a pressure responsive valveinterposed between said booster chamber and said main cylinder and beingbiased to closed position; and a hydraulic connection between saidpressure responsive valve and said ram-returning chamber for supplyinguid under pressure to the valve to open the latter during a returnstroke.

6. The combination with a hydraulic press including a platen, a maincylinder and cooperating main ram connected to said platen, an auxiliarycylinderhaving booster and ram-returning chambers, a double-actingauxiliary ram therein, and a connection between said auxiliary ram andsaid platen extending through said ram-returning chamber; of areservoir; a surge valve connected between said main cylinder andreservoir; a pump; a hydraulic connection between said pump and saidram-returning chamber; a second hydraulic connection between said pumpand said booster chamber; a valve interposed between said boosterchamber and said main cylinder; a yieldable means for urging saidlastnamed valve to closed position; platen actuated means for openingsaid valve during part of a pressing stroke; and means responsive topressure in said returning chamber .for holding said valve open during areturn stroke.

7. The combination with a hydraulic press including a platen, a maincylinder and cooperating main ram connected to said platen, an auxiliarycylinder having booster and ram-returning chambers, a double-actingauxiliary ram therein, and a connection between said auxiliary ram andsaid platen extending through said ram-returning chamber; of areservoir; a surge valve connected between said main cylinder andreservoir; a pump; a hydraulic connection between said pump and saidram-returing chamber; a

second hydraulic connection between said pump and said booster chamber;means responsive to pressure in said returning chamber for opening saidsurge valve; and a valve interposed between said booster chamber andsaid main cylinder and being adapted to be held open by pressure in saidram-returning chamber during a return stroke.

8. The combination with a hydraulic press including a platen, a maincylinder and cooperating main ram connected to said platen, anauxiliary;v

cylinder having booster and ram-returning chambers, a double-actingauxiliary ram therein, and a connection between said auxiliary ram andsaid platen extending through said. ram-returning chamber; of areservoir; a surge valve connected|g between said main cylinder andreservoir; a pump; a hydraulic connection between said pump and saidram-returning chamber; a second hydraulic connection between said pumpand said booster chamber; means responsive to pressure;

-in said returning chamber for opening said surge lvalve; a valveinterposed between said booster -chamber and said main cylinder andbeing adapted to be held open by pressure in said ram-returning chamberduring a return stroke; a pressure release valveconnected between saidmain cylinder and said reservoir and being operable to op'en position bypressure in said returning chamber; and a by-pass valve connectedbetween said returning chamber and said reservoir and being operable toopen position by pressure in said main cylinder.

`9i The combination with a hydraulic press including a platen, a maincylinder and cooperating main ram -connected to said platen, auxiliarycylinder means having booster and ram-returning chambers, andcooperating auxiliary ram means therein, said booster chamber being ofgreater capacity than vsaid ram-returning chamber; of a reservoir; asurge valve connected between said main cylinder and reservoir; a pump;a hydraulic connection 'between said pump and said ram-returningchamber; a second hydraulic connection between -said pump and saidbooster chamber; a pressure responsive valve interposed between saidbooster chamber and said main cylinder and being biased to closedposition; and a hydraulic connection between said pressure responsivevalve and said ram-returning chamber for supplying -uid under pressureto the valve to open the latter during a return stroke.

10. l'The combination with ahydraulic press including cylinder meanshaving pressing and ramreturning chambers and ram means mounted therein-for reciprocatory movements; of a pump;

with said cylinder means for furnishing pressure fluid to said chambers;a reservoir; a surge valve for controlling communication between saidreservoir and pressing chamber; and release valve means for relievingpressure in said pressing chamber at a controlled low rate forfacilitating opening of said surge valve, said means including arestricted vpassage between said pressing chamber and said reservoir ofsuch small size as to present sufficient resistance to flow of fluid toretard the flow substantially, thereby preventing water hammer, andmeans connected to said release valve means and being responsive-to anlincrease in pressure in said ram-returning chamber for moving saidrelease valve to open position.

12. The combination with a hydraulic press having cylinder meansincluding a pressing chamber and a ram returning chamber and cooperatingram means mounted therein; of a pump;

means connecting said pump with said chambers for furnishing pressurefluid thereto; .a reservoir; a surge valve for controlling relativelyopen communication between said reservoir and said pressing chamber;-means for relieving pressure in said pressing chamber ata controlled rowrate includingra restricted passage between said chamber andsaidreservoir of such small size as to Vpresent sufficient resistance toflow of iiuid to retard the ow substantially, thereby .preventing waterhammer;

.and a valve controlled by-pass between said returning chamber andsaidreservoir.

13. The combination with a hydraulic press having cylinder meansincluding Vpressing and ram-returning chambers and -cooperating rammeans mounted therein; of a pump; means connecting said pump with saidcylinder means for furnishing pressure uid to said chambers; areservoir; a surge valve -for controlling communication between saidreservoir and pressing chamber; a pressure release valve connected tosaid pressing chamber for eiecting release of pressure uid from saidpressing cylinder prior to opening of saidsurge valve; and a by-passvalve connected between vsaid returning chamber and said reservoir foreffecting discharge of the pump to the reservoir during release ofypressure from said pressing chamber and prior to opening .of said surgevalve.

WALTER ERNST.

